1. Field of the Invention
This invention relates to a method of processing smoking composition, more particularly, it relates to the method of processing smoking composition so as to improve the water-resistance of the same for a certain period.
The term "smoking composition" in the present specification and claims refers to a so-called reconstituted tobacco or a tobacco substitute having been prepared by such a method that natural tobacco material and/or organic or inorganic material(s) which are combustible are admixed with binder, humectant, burning regulator, reinforcing agent, flavourant and the like, followed by forming the resultant mixture into a sheet-like or rod-like shape. All percentages and parts in the specification and claims are by weight.
It has hitherto been known several methods for preparing said smoking compositions or reconstituted tobaccos in which natural tobacco material such as tobacco leaf, tobacco dust, tobacco waste or tobacco powder has been used as main raw materials (cf. Japanese patent publication Nos. 25750/1963, 25719/1971, 10040/1972, 10560/1973).
Recently, in view of the smoking-and-health as well as liking of smokers, cigarettes which produce smoke containing less nicotine and tar are rather preferred to those producing smoke containing more such constituents for smokers. Following the above preference of smokers, there have been proposed several preparations of tobacco substitutes in which organic and/or inorganic material(s) that are combustible have been substituted partially or wholly for the natural tobacco material which is the main raw material of reconstituted tobacco (cf. Japanese publication Nos. 27357/1971, 16960/1974).
The above-mentioned smoking compositions, that is, the reconstituted tobacco and tobacco substitute are submitted to the production of cigarettes, pipe tobaccos, cigars and the like (these are hereinafter called "smoking products" in the lump), where said compositions are somewhat humidified and added hydrous solution of suitable additives thereto in order to improve the processability therein and further to improve the organoleptic properties of the smoking products having been made with said compositions.
Thus, the smoking composition which is the main raw material of the smoking products is required to have a considerable water-resistance so that the external shape of the composition will not be broken in the course of said humidifying and addition of hydrous solution of additives, said water-resistance of the smoking composition depending principally on the physical properties of the binders having been used for the preparation of smoking composition.
However, on the other hand, such binders of the smoking composition are needed reversely to be somewhat water-soluble in relation to the processability at the preparation of smoking composition itself using the said binders.
Because of the above-mentioned two requirements of the binder which are inconsistent with each other, the smoking composition prepared using such binder cannot but has comparatively low water-resistance generally, whereby several kinds of troubles have been caused at said humidifying step and the like of the smoking products production.
Water-solubility of the binders of smoking composition such as the cellulose derivatives (ethyl cellulose, methyl cellulose, hydroxy cellulose, carboxymethyl cellulose, etc.) and the starch derivatives (methyl starch, ethyl starch, carboxymethyl starch, hydroxy starch, etc.) depends mainly on the degrees of polymerization and of substitution by ether groups (hereinafter abbreviated to D.P. and D.S respectively), and while, among others, sodium carboxymethyl cellulose (hereinafter abbreviated to CMC-Na) is regarded as the most suitable facility of industrial production thereof, water-solubility and the like, the smoking composition prepared by using CMC-Na has the shortcoming that its water-resistance is lower than those of the compositions prepared by using other binders.
2. The Prior Art
In order to improve generally the water-resistance of smoking composition, there have been proposed several methods in which the cross-linking agents such as glyoxal, dimethylol ureaformaldehyde resin, melamine formaldehyde resin, dialdehyde starch, metallic salts of organic acids or halides have been used together with cellulose derivatives or starch derivatives that have generally been used as binder.
However, the smoking compositions thus prepared by using said cross-linking agents together with the binders have been regarded as to be considerably undesirable in view of the organoleptic properties as well as smoking-and-health of the smoking products prepared therewith.